Island populations often differ in consistent ways from their mainland counterparts with respect to their ecology, behaviour, morphology, demography and life-history characteristics; a set of changes referred to as the 'island syndrome'. To understand the ecological and evolutionary drivers of the island syndrome requires characterization of suites of interacting traits. While patterns in some types of traits, e.g. body size, are well characterized across a range of taxa, key gaps remain. Growth rate is one such trait, being an important determinant of both increases and decreases in body size, and can vary with changes in predation pressure and food limitation; two factors that are known to differ between mainland and island environments. Using a phylogenetic meta-analytic approach, we characterize differences in growth rates among mainland and island altricial bird populations, controlling for environmental factors. We found a trend towards slower growth on islands in small-bodied (less than 1 kg) bird species. This is consistent with the idea that the pattern of body size increases in small-bodied island colonists is associated with the evolution of slower growth combined with shifts in age and size at maturity in relaxed predation regimes.
Understanding the influence of environmental factors on population dynamics is fundamental to many areas in biology. Survival is a key factor of population biology, as it is thought to be the predominant driver of growth in long-lived passerines, which can be influenced by both biotic and abiotic environmental conditions. We used mark-recapture methods and generalized linear mixed models to test the influence of density and climatic variation, measured at a regional and local scale (Southern Oscillation Index [SOI] and rainfall, respectively), on seasonal variation in survival rates of an insular population of Silvereyes (Zosterops lateralis chlorocephalus), during a 15-year study period, off the east coast of Australia. We found overall high survival rates for adults and juveniles (81% and 59%, respectively). Local scale climate (i.e. rainfall) and density were the principal environmental factors influencing their survival, both with a negative relationship. A significant interactive effect of density and rainfall influenced survival as they both increased. However, survival remained low when density was at it highest, independent of the amount of rainfall. Nestling survival was negatively influenced by rainfall and density, positively by SOI, and chicks that hatched later in the breeding season had higher survival rates. The regional scale climate variable (i.e. SOI) did not explain survival rates as strongly as rainfall in any age class. Our results contribute to the understanding of insular avian population dynamics and the differential effects of environmental factors across age classes. Climatic predictions expect El Niño events to increase, meaning dryer conditions in eastern Australia, potentially increasing Silvereye survival across age classes. However, the long-term effect of lower rainfall on food availability is unknown; consequently, the outcome of lower rainfall on Silvereye survival rates is uncertain.
Free-roaming dogs are a worldwide problem, with Chile having some of the highest human-to-dog ratios in the world. In 2017, Law 21.020 was promulgated and the federal government developed a national responsible pet ownership program. The objectives of this article are to describe and discuss the dog-related components of the program, to design a tool for determining human-to-dog ratios in Chile, and to make recommendations to managers to improve the program outcomes. The overarching goal of the program was to mitigate the conflict between humans and dogs, but many of the interventions were animal-focused and the indicators did not consider the perception of the Chilean public. Using human density data and known dog populations, we found that as the human density increased, there were fewer dogs per person. Veterinary services and sterilizations were the mainstay of the program and were offered for free to citizens. Education was offered to all ages through public events, as well as municipality and organization activities. The identification of dogs was obligatory for dog owners. Enforcement was not included in the program. The recommendations are to conduct preintervention baseline data collections and to tailor interventions and indicators appropriately; to use dog population size estimates determined at the local level rather than a country-wide estimate; to replace free veterinary services with low-cost sterilization campaigns; to create sustainable plans for education; and to create enforcement teams in communities.
The creation of protected areas has been the main strategy to counter loss and fragmentation of habitats for large mammals, but these areas by themselves cannot guarantee species' conservation. Forestry plantations can provide habitat for a large range of species. However, studies assessing the impact of forestry plantations on large mammals are scarce. Our objective was to identify the environmental variables that explained the presence of the endangered huemul deer (Hippocamelus bisulcus) in an area with mixed pine plantation and native forest in the Chilean Patagonia. Occupancy models using data collected from camera traps indicated higher occupancy in plantation areas (0.70) than in native forest (0.50). The main variable explaining the presence of the huemul in both forest types was the understory cover between 21 cm and 50 cm in height. By maintaining understory cover, plantations provide a suitable complementary habitat for the forest-dwelling huemul. Ó 2016 The Wildlife Society.
A natural laboratory is a place supporting the conditions for hypothesis testing under non-anthropogenic settings. Located at the southern end of the Magellanic sub-Antarctic ecoregion in southwestern South America, the Cape Horn Biosphere Reserve (CHBR) has one of the most extreme rainfall gradients in the world. Subject to oceanic climate conditions, it is also characterized by moderate thermal fluctuations throughout the year. This makes it a unique natural laboratory for studying the effects of extreme rainfall variations on forest bird communities. Here, we monitor the bird species richness in the different forest types present in the CHBR. We found that species richness decreased with increasing precipitation, in which an increase of 100 mm in average annual precipitation showed about 1% decrease in species richness. Similar patterns were found among different forest types within the CHBR. These results provide a baseline to investigate the interactions between physical and biotic factors in a subpolar region that climatically contrasts with boreal forests, which is subject to continental climatic conditions. This research highlights the importance of ecological and ornithological long-term studies in the CHBR, which can contribute both to a higher resolution of the heterogeneity of climate changes in different regions of the world, and to orient conservation policies in the Magellanic sub-Antarctic ecoregion in the face of growing development pressures.
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